Method for Monitoring the Energy Content of a Water Storage Tank System

ABSTRACT

A method of controlling a heat up of a hot water tank, comprising a tank, which contains water and receives incoming cold-water at a cold-water inlet and outputs heated water through a heated water outlet, the method comprising: heating the water in the tank depending on a thermal energy content calculated as a function of an actual incoming cold-water temperature measured by a cold-water temperature sensor, when a tapping event is identified. A water tank heating device and a controller system for controlling a heat up of a hot water tank depending on a thermal energy content calculated as a function of an actual incoming cold-water temperature.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of U.S. application Ser. No.16/040,665, filed Jul. 20, 2018, which is incorporated herein byreference in its entirety.

FIELD OF THE INVENTION

The present disclosure relates to a method for monitoring the energycontent of a water storage tank system.

It is noted that citation or identification of any document in thisapplication is not an admission that such document is available as priorart to the present disclosure.

Future demand controlled grid systems need information about the energyquantity of storage systems for peak shaving and net stabilizationreasons. In particular, the storage capacity of electric heated watertank systems is important for grid stabilization when consideringelectric energy generation from wind and solar sources.

Introducing a demand controlled water heating system makes it possibleto optimize the power generation when under considering low cost powerdistribution and grid stability. In the future consumers can offer theirwater storage tank capacities to utilities to store thermal energy intimes when wind and solar energy is abundant. Current state of the artis to provide an information about the temperature in a water tank usinga capillary tube, which contains a heat sensitive fluid in contact withthe water tank. U.S. Pat. No. 2,009,100 199 31 A1 provides informationabout such a system.

DE 10 2010 047 368 B3 shows a method of controlling a water storage tankheated with an electric element. The heat up time for the water storagetank is based on information about the consumer's history of withdrawalusing different supercharging rates for temperature settings.

Both methods are expensive and/or not accurate in order to supply exactinformation about useful energy content in the water storage tank.

DE 10 2004 018 034 B4 shows a heat pump connected to a hot water storagesystem with a cold-water inlet in the lower part and a hot water supplyin the upper section, linked by a heat exchanger. A temperature sensoris located in the lower part of the tank. Alternatively, an impellerflow meter is located in the water pipe. The sensor or flow metertriggers operation of the heat pump if the amount of tapped water ismore than a defined threshold value.

SUMMARY OF THE INVENTION

Provided is a method of controlling a heat up of a hot water tank,comprising a tank, which contains water and receives incoming cold-waterat a cold-water inlet and outputs heated water through a heated wateroutlet, a heating device and a controller system to control said heatingdevice, the method comprising: heating the water in the tank by saidheating device, depending on a thermal energy content calculated, by acontrol unit of said controller system, as a function of an actualincoming cold-water temperature measured with a cold-water temperaturesensor of said controller system, when a tapping event is identified.

Preferably the method can comprise the steps of:

identifying, by a control circuit arrangement of said control unit, atapping event,

measuring said incoming cold-water temperature with said cold-watertemperature sensor,

receiving, by a receiving interface circuit of said control unit, anactual incoming cold-water temperature signal generated and transmittedby said temperature sensor, which represents said incoming cold-watertemperature,

calculating, by said control circuit arrangement of said control unit,said thermal energy content as a function of said actual incomingcold-water temperature,

generating, by said control circuit arrangement of said control unit, anactivation signal to activate a heating device depending on said thermalenergy content,

transmitting, by a transmitter interface circuit of a control circuit,said activation signal to a receiver interface circuit of said heatingdevice.

In a preferred embodiment said tapping event is identified by measuringsuccessive incoming cold-water temperatures in successive cold-watertemperature measurements with said cold-water temperature sensor anddetecting a beginning of said tapping event when a difference of twosuccessive incoming cold-water temperatures of two successive cold-watertemperature measurements is more than 2° C.

Preferably, the control unit, in particular the control circuitarrangement, is configured to perform a comparison of said successiveincoming cold-water temperatures to detect said tapping event.

Preferably said actual incoming water temperature is measured in anadequate time period during said tapping event, in which said actualincoming cold-water can be measured.

Said “adequate time period” describes a period in which said actualincoming cold-water temperature can be measured. Before this adequatetime period, an incoming cold-water temperature can be higher or lowerthan said actual incoming cold-water temperature, for example caused bystoring the incoming cold-water in the inlet pipe before the tappingprocess.

Preferably said adequate time period starts after a defined period fromsaid beginning of said tapping event.

Preferably, said defined period is 20 seconds.

Preferably said adequate time period ends after more than 30 seconds orat or after an end of said tapping event.

Preferably, the method further comprises: comparing, by said controlunit, said successive incoming cold-water temperatures, measured in adefined measuring rate, wherein said adequate time period starts when adifference of two successive incoming cold-water temperatures of twosuccessive cold-water temperature measurements is less than 1° C.

Preferably, the method further comprises measuring successive incomingcold-water temperatures in successive cold-water temperaturemeasurements with said cold-water temperature sensor during saidadequate time period, storing said successive cold-water temperatures ina storing unit and averaging, by said control unit, said successivecold-water temperatures stored in said storing unit to obtain anaveraged incoming cold-water temperature, which is used as said actualincoming cold-water temperature.

Preferably, the method further comprises determining, by said controlunit, a validity of said depending on said difference, wherein saidsuccessive cold-water temperature measurements are valid if saiddifference is lower than a defined difference value.

Preferably, the method further comprises measuring a tank temperature,which is related to a thermal energy content, and output a tanktemperature signal representative of said tank temperature with a tanktemperature sensor mounted to said tank.

Provided is further a hot water tank heating system, comprising a tankto contain water with a water inlet configured for receiving incomingcold-water and a water outlet configured for allowing water heated toexit, a heating device to heat the water in the tank and a controllersystem with

-   -   a cold-water temperature sensor attached at a place and        configured to measure an actual incoming cold-water temperature        and to output an actual cold-water temperature signal        representative of said actual incoming cold-water temperature        and    -   a control unit comprising microprocessor software integrated in        an electronic device,    -   wherein said control unit is configured to receive said actual        cold-water temperature signal transmitted by said cold-water        temperature senor, and    -   wherein said control unit is configured to identify a tapping        event and to control the heating device when said tapping event        is identified in order to heat water in the tank depending on a        thermal energy content calculated as a function of said actual        incoming cold-water temperature measured by said cold-water        temperature sensor.

“Output an actual cold-water temperature signal” can preferably includegenerating an actual cold-water temperature signal.

Preferably, the hot water tank heating system comprises a cold-waterpipe connected to the water inlet and a heated water pipe connected tothe water outlet.

Preferably, the control unit comprises a control circuit arrangement, areceiver interface circuit for receiving signals and a transmitterinterface circuit for transmitting signals. Preferably, the control unitfurther comprises a storage unit to store signals or the control unit iscoupled to a storage unit to store signals.

Preferably, the hot water tank heating system comprises a tanktemperature sensor mounted to said tank configured to measure a tanktemperature, which is related to a thermal energy content, and output atank temperature signal representative of said tank temperature, whereinsaid control unit is configured to receive said tank temperature signaltransmitted by said tank temperature sensor.

In a preferred embodiment, the cold-water temperature sensor can belocated proximate to said water inlet.

In a preferred embodiment, the cold-water temperature sensor can bemounted to an inner surface of said tank or an inner surface of acold-water pipe connected to the water inlet.

In a preferred embodiment, the cold-water temperature sensor can bemounted to an outer surface of said tank or an outer surface of acold-water pipe connected to the water inlet.

Provided is further a controller system for controlling a heat up of ahot water tank, comprising

-   -   a cold-water temperature sensor configured to be attached at a        place of a tank, which contains water and comprises a water        inlet configured for receiving incoming cold-water and a water        outlet configured for allowing water heated to exit,    -   wherein said cold-water temperature sensor is configured to        measure an actual incoming cold-water temperature and to output        an actual cold-water temperature signal representative of said        actual incoming cold-water temperature and    -   a control unit comprising microprocessor software integrated in        an electronic device,    -   wherein said control unit is configured to receive said actual        cold-water temperature signal transmitted by said cold-water        temperature senor,    -   wherein said control unit is configured to identify a tapping        event and to control a heating device when said tapping event is        identified in order to heat water in the tank depending on a        thermal energy content calculated as a function of an actual        incoming cold-water temperature measured by said cold-water        temperature sensor.

Provided is further a method of controlling a heat up of a hot watertank having a control unit where a tank temperature is measured and thetank temperature is fed into a control unit. A heating element isactivated to heat up warm water in the tank when the control unit callsfor heat. An incoming cold-water temperature is fed into the controlunit and it generates a parameter effected by this incoming cold-watertemperature. The tank temperature measured is related to the thermalenergy content of the tank. The tank temperature is measured with awater temperature sensor mounted to the tank, further affecting theparameter with the tank temperature. A call for heat is processeddepending on a comparison of a set point value with the parameter, whichis generated from the tank temperature and the measured cold-watertemperature.

Preferably, the method of controlling a heat up of a hot water tankhaving a control unit with a receiver interface circuit, a controlcircuit arrangement and a transmitter interface circuit, the methodcomprising the steps of:

measuring a first tank temperature of said hot water tank with atemperature sensor mounted to said hot water tank;

receiving, by said receiver interface circuit, a first tank temperaturesignal generated and transmitted by said temperature sensor, whichrepresents said first tank temperature;

generating, by said control circuit arrangement, an activation signal toactivate a heating device, when said control circuit arrangement callsfor heat;

feeding an actual incoming cold-water temperature signal into saidcontrol circuit arrangement, wherein said actual incoming cold-watertemperature signal represents an actual in-coming cold-water temperatureof cold-water, which flows into said hot water tank;

generating, by said control circuit arrangement, a parameter based onsaid actual incoming cold-water temperature signal;

measuring a second tank temperature of said hot water tank with saidtemperature sensor after said incoming cold-water flowed into said hotwater tank, wherein said second tank temperature is related to a thermalenergy content of said hot water tank;

receiving, by said receiver interface circuit, a second tank temperaturesignal generated and transmitted by said temperature sensor, whichrepresents said second tank temperature;

modifying, by said control circuit arrangement, said parameter based onsaid second tank temperature signal;

performing, by said control circuit arrangement, a comparison of a setpoint value with said parameter, which is modified based on said secondtank temperature signal;

processing, by said control circuit arrangement, said activation signaldepending on said comparison; and

transmitting, by said transmitter interface circuit to a receiverinterface circuit of a heating device, said activation signal, which isprocessed depending on said comparison.

A “call for heat” can preferably be understood as a request to activatethe heating device.

“Mounted to the tank” means that this sensor could be mounted inside thetank or outside the tank. If it is mounted outside the tank this sensoris especially mounted on an outer surface of the tank.

Preferably, the method comprises the steps of:

calculating, by said control circuit arrangement, an exact value of saidthermal energy content as a function of a reference mass and saidparameter, which is modified based on said second tank temperaturesignal,

wherein the step of generating, by said control circuit arrangement,said activation signal depends on whether said exact value is lower thansaid set point value,

wherein said control circuit arrangement generates said activationsignal when said exact value is lower than the set point value.

Preferably, it is foreseen to supply permanently exact information ofthe energy content of the water storage tank system to a utility inorder to meet the requirements of consumer comfort and the utility tosave costs and stabilize the grid.

Preferably, the method comprises the step of calculating an exact valueof thermal energy content as a function of reference mass and thegenerated parameter.

Preferably, the method comprises the step of calculating an exact valueof thermal energy content as a function of reference mass and themodified parameter.

Preferably, the method comprise the step to measure the internal watertemperature of the tank via an integral temperature sensor.

Preferably, the tank temperature is measured with an integraltemperature sensor.

Additionally, a further embodiment describes a call for heat when theexact temperature value is less than the set point value.

Preferably, the step of activating the heating device depends on theamount of the calculated exact value.

In an embodiment, the step of activating the heating element followswhen the amount of the calculated exact value is less than a specifiedvalue of thermal energy content.

Preferably, the method comprises: calculating, by said control circuitarrangement, an exact value of said thermal energy content as a functionof a reference mass and said parameter, which is modified based on saidsecond tank temperature signal, wherein the step of generating, by saidcontrol circuit arrangement, said activation signal depends on an amountof said exact value.

Preferably, the step of generating, by said control circuit arrangement,said activation signal depends on whether said amount of said exactvalue is lower than a specified value of thermal energy content, whereinsaid control circuit arrangement generates said activation signal whensaid amount of said exact value is less than a specified value ofthermal energy content.

Further, it is preferred to calculate the exact value of thermal energycontent by multiplying the reference mass parameter by a temperaturerise value.

Preferably, the temperature rise is the difference between the set pointtemperature and the incoming cold-water temperature.

According to a further embodiment, it is described to compare themeasured actual cold-water temperature signal with a previous storedcold-water temperature, to update the actual cold-water temperaturesignal if it is different than a previous one and to use the updated oneto calculate the parameter. Therefore, the method comprises the stepsof: comparing a measured actual cold-water temperature signal with aprevious stored cold-water temperature; updating the stored cold-watertemperature value if the measured actual cold-water temperature signalis different from the previous stored cold-water temperature; andutilizing the updated stored cold-water temperature value to calculatethe parameter.

Preferably, wherein the stored cold-water temperature value is updatedwhen the actual cold-water temperature signal is lower than the previousstored cold-water temperature.

In an embodiment, the method comprises the step of updating, if theactual cold-water temperature signal is different than a defined value.

According to a further embodiment, a step is described identifying atapping event to detect the actual cold-water temperature in an adequatetime period after a tapping begins.

According to a further embodiment, a step is described of detecting thecold-water temperature in an adequate time period, wherein an adequatetime period begins after the end of an inadequate time period.

Said “inadequate time period” describes a period in which successiveincoming cold-water temperatures can vary greatly. In particular, theycan vary from said actual incoming cold-water temperature, for examplecaused by storing the incoming cold-water in the inlet pipe before thetapping process.

According to a further embodiment, a step is described for determiningthe inadequate time period when the time frame is exceeded.

According to a further embodiment, a step is described for determiningthe time frame of approximately 5 to 40 seconds, in particular 20seconds.

In an embodiment, the adequate time period starts with the end of theinadequate time period and ends after more than 30 seconds, or at theend of the tapping event.

In an embodiment, the method comprises the step of comparison of asuccessive cold-water temperature with differences using the sensortemperature information and a time base.

According to a further embodiment it is described to detect the tappingbegin if the difference of two successive cold-water temperature valuesis more than 2 K during the first time base.

According to a further embodiment, a step is described to start a firsttimer 1 with an inadequate time period.

According to this embodiment, it follows the step of comparison anactual cold-water temperature with a previous one to calculate adifference. If the difference is less than a special parameter, a timertwo is activated to measure the actual cold-water temperatureinformation via the temperature sensor during a time base.

According to a further embodiment there are described steps to detect,after second timer 2 is started, the incoming cold-water temperaturefrequently for a minimum duration between 5 to 30 seconds, in particularmore than 10 seconds, to put each single following cold-watertemperature value in a register, and compare the successive measuredvalues. If a difference of less than a second parameter exists, themeasurement is valid.

It is preferred to average the cold-water temperature values in theregister, compare an actual averaged cold-water temperature with theformer stored averaged value, and if the difference of the actualcalculated value compared to the former stored value is more than 2 K,the former stored value is updated using a simple moving averagingprocess to avoid any jumping of values on a display.

According to a further embodiment, it is described to identify a tappingevent with an adequate time period in order to detect the actualcold-water temperature by comparison of previous cold-water temperaturevalues with the measured actual cold-water temperature signal, storing alowest value of cold-water temperature of the previous cold-watertemperature values and the cold water temperature measured actualcold-water temperature signal, and using the stored lowest value tocalculate the exact value of thermal energy.

According to a further embodiment, a step is described in which theenergy needs of at least one tank is provided or sent to an energysupplier.

According to this embodiment, it follows the step for utilities to sortthe consumers into different energy demand classes in order to stabilizethe voltage or frequency of the grid.

According to a further embodiment comprises a step that the waterheating unit can be remotely controlled by the utility.

In an embodiment the usable hot water temperature range is between 30°C. to 50° C.

In an embodiment, the lowest usable hot water temperature is close to40° C.

In an embodiment, a disinfection hot water temperature is close to 55°C., 60° C. or more.

The disinfection hot water temperature is especially activated dependingon an amount of tapped water in a time period.

According to a further embodiment, the heating element is an electricheating element.

According to a further embodiment, the heating device is a heatexchanger of a heat pump or the tank is connected to a heat pump orrefrigerant circuit. The heat pump is activated when the electronicdevice or a thermostat calls for heat.

According to a further embodiment, the content of the water heater mustbe tapped or renewed in a specific time period.

According to a further embodiment, the time to renew or tap the contentof the tank could be three days.

According to a further embodiment the set temperature of the water inthe tank is reduced to a lower temperature than 60° C., especially to55° C. or less.

The available amount of mixed water is an important piece of informationfor the consumer and depends on the tank volume, mixing effect in thecold bottom of the tank below the element, and of course the expectedhot water temperature and the temperature of the cold incoming water.For example, if the expected hot water temperature in the tank is 85° C.at 100-liter heated tank volume and the usable water temperature is 40°C. for 15° C. and 10° C. incoming cold-water temperature, the amount ofmixed water is calculated, equation [0]:

In numbers, equation [1]:

$\begin{matrix}{{M_{m} = \frac{{Mhw}*\left( {T_{sw} - T_{cw}} \right)}{T_{mw} - T_{cw}}}{M_{m}\mspace{14mu} {amount}\mspace{14mu} {of}\mspace{14mu} {mixed}\mspace{14mu} {water}}{T_{mw}\mspace{14mu} {Mix}\mspace{14mu} {Water}\mspace{14mu} {temperature}}{M_{hw}\mspace{14mu} {available}\mspace{14mu} {heated}\mspace{14mu} {tank}\mspace{14mu} {volume}}{T_{sw}\mspace{14mu} {Expected}\mspace{14mu} {hot}\mspace{14mu} {water}\mspace{14mu} {temperature}\mspace{14mu} \left( {{set}\mspace{14mu} {point}} \right)}{T_{cw}\mspace{14mu} {Temperature}\mspace{14mu} {incoming}\mspace{14mu} {cold}\text{-}{water}}} & {{Equation}\mspace{14mu}\lbrack 0\rbrack} \\{{M_{m15} = {\frac{100l*\left( {{85} - {15}} \right)\left( {{^\circ}\mspace{14mu} {C.}} \right)}{{40} - {15\left( {{^\circ}\mspace{14mu} {C.}} \right)}} = {280\; l}}}{M_{m\; 10} = {\frac{100l*\left( {{85} - {10}} \right)\left( {{^\circ}\mspace{14mu} {C.}} \right)}{{40} - {10\left( {{^\circ}\mspace{14mu} {C.}} \right)}} = {250l}}}} & {{Equation}\mspace{14mu}\lbrack 1\rbrack}\end{matrix}$

In this example, the amount of useful water is reduced by more than 10%if the variation of incoming cold-water is more than 5 K. A 5 Kvariation of the incoming cold-water temperature is a good average valueif the seasonal ambient temperature between summer and winter season istaken into account.

In addition, there is a variation of the annual average incomingcold-water temperature depending on the geographic location.

In another embodiment, tank data is provided to utilities where a needof electric energy is calculated for heat up time.

With this, data from different tank systems utilities can remotelycontrol the tanks and define the heat up start or activation of theheating device.

Herewith a load shifting is possible on the utility's grid, especiallyto control the network voltage or network frequency.

In a preferred embodiment the method comprises: calculating, by saidcontrol circuit arrangement, an exact value of said thermal energycontent by multiplying a reference mass parameter by a temperature risevalue, wherein said temperature rise value is a difference between saidset point value and said actual incoming cold-water temperature, whereinthe step of generating, by said control circuit arrangement, saidactivation signal depends on said exact value.

Preferably, the method further comprises: comparing, by said controlcircuit arrangement, said actual incoming cold-water temperaturerepresented by said actual cold-water temperature signal fed into saidcontrol circuit arrangement with a previous stored water temperaturerepresented by a previous stored water temperature signal, which isstored in a storage circuit of said control circuit arrangement;updating, by said control circuit arrangement, said previous storedwater temperature signal, if said actual incoming cold-water temperaturediffers from said previous stored water temperature; and utilizing saidstored water temperature signal, which is updated, for the step ofgenerating, by said control circuit arrangement, said parameter.

Preferably, the step of updating, by said control circuit arrangement,said previous stored water temperature signal, depends on whether saidactual incoming cold-water temperature is lower than said stored watertemperature, wherein said control circuit arrangement updates saidprevious stored water temperature signal if said actual incomingcold-water temperature is lower than said previous stored watertemperature.

Preferably, the step of updating, by said control circuit arrangement,said previous stored water temperature signal, depends on whether saidactual incoming cold-water temperature is different from a definedvalue.

Preferably, wherein the step of feeding said incoming cold-watertemperature signal into said control circuit arrangement, comprises thesteps: measuring said actual incoming cold-water temperature with acold-water temperature sensor located in said hot water tank close to awater inlet; and receiving, by said receiver interface circuit, saidactual incoming cold-water temperature signal generated and transmittedby said cold water temperature sensor, which represents said actualincoming cold-water temperature.

Preferably, the method further comprises: identifying a tapping event inorder to detect said actual incoming water temperature within anadequate time period after a tapping begins.

Preferably, the method further comprises: detecting said actual incomingcold-water temperature within said adequate time period.

Preferably, said adequate time period starts after a defined period froma beginning of said tapping event.

Preferably, said defined period is 20 seconds.

Preferably said adequate time period starts after a defined period froma beginning of said tapping event and ends after more than 30 seconds orat or after an end of said tapping event.

Preferably the step of detecting the actual incoming cold-watertemperature within said adequate time period further comprises the stepsof: measuring successive incoming cold-water temperatures in successivecold-water temperature measurements; and performing, by said controlcircuit, a comparison of said successive cold-water temperaturemeasurements using differences between said successive incomingcold-water temperatures and information of a time base, which controls ameasuring rate.

Preferably, the method further comprises: detecting a beginning of saidtapping event when a difference of two successive incoming cold-watertemperatures of two successive cold-water temperature measurements ofmore than 2 K results from said comparison of said successive cold-watertemperature measurements.

Preferably, the method further comprises: starting a first timer at saidbeginning of said tapping event to detect a period after which saidadequate time period starts.

Preferably, the method further comprises: comparing a last measuredincoming cold-water temperature with a previously measured incomingcold-water temperature to calculate a difference; and activating asecond timer, which initiates detecting said actual incoming cold-watertemperature or successive incoming cold-water temperatures with a timebase, when said difference is lower than a first defined differencevalue.

Preferably, the method further comprises: after said second timer isstarted, detecting successive incoming cold-water temperaturesperiodically for a minimum duration of more than 10 seconds and puttingeach incoming cold-water temperature in a register; performing, by saidcontrol circuit arrangement, a comparison of said successive incomingcold-water temperatures putted in said register; and determining, bysaid control circuit arrangement, a validity of said successivecold-water temperature measurements depending on a difference resultingfrom said comparison, wherein said successive cold-water temperaturemeasurements are valid if said difference is lower than a second defineddifference value.

Preferably, the method further comprises: averaging, by said controlcircuit arrangement, the successive incoming cold-water temperaturesputted in said register to obtain an averaged incoming cold-watertemperature; comparing, by said control circuit arrangement, saidaveraged incoming cold-water temperature with a previous stored averagedwater temperature represented by a previous stored averaged watertemperature signal, which is stored in a storage circuit of said controlcircuit arrangement; and updating, by said control circuit arrangement,said previous stored averaged water temperature signal, if a differencebetween said averaged incoming cold-water temperature and said previousstored averaged water temperature is more than 2 K, wherein the step ofupdating, by said control circuit arrangement, said previous storedwater temperature signal comprising a simple moving averaging process.

Preferably, the method further comprises: identifying a tapping eventwith a adequate time period in order to detect said actual incomingwater temperature by comparing, by said control circuit arrangement,previously measured incoming cold-water temperatures with an lastmeasured incoming cold-water temperature; storing, by said storagecircuit, a first temperature signal, which represents a lowesttemperature of said previously measured incoming cold-watertemperatures, and a second temperature signal, which represents the lastmeasured incoming cold-water temperature; and utilizing said firsttemperature signal to calculate an exact value of said thermal energycontent of said hot water tank.

Preferably, the method further comprises: providing energy needs of atleast one hot water tank to an energy supplier or transmitting energyneeds of at least one hot water tank to a utility company.

Preferably, a utility company sorting consumers into different energydemand classes in order to stabilize a voltage to keep said voltageconstant, a frequency to keep said frequency constant, or both, of anelectric grid.

Preferably, the heating device comprises a receiver interface circuit toreceive a remote control command, which is generated and transmitted bya utility company, wherein the method comprises the step of receiving,by said receiver interface circuit of the heating device, said remotecontrol command generated and transmitted by said utility company.

Preferably, said temperature sensor for measuring said first tanktemperature and said second tank temperature of said hot water tank ismounted on an outer surface of said hot water tank.

Preferably, wherein said temperature sensor for measuring said firsttank temperature and said second tank temperature of said hot water tankis mounted on an inner surface of said hot water tank.

In an aspect, the disclosure relates to a method of determining athermal energy content of a hot water tank device, the hot water tankdevice comprising a tank, a cold-water inlet, a heated water outlet, acold-water temperature sensor, a heating device and a controllercomponent, the tank containing water, wherein the tank receives incomingcold-water at the cold-water inlet and outputs heated water through theheated water outlet when a tapping event occurs, the heated water outletbeing located in an upper portion of the tank and the cold-water inletbeing located in a lower portion of the tank with the heating devicebeing thermally coupled to water in between the cold-water inlet and theheated water outlet, the cold-water temperature sensor being arranged inthe lower portion of the tank configured to determine a temperature ofthe water in vicinity of the cold-water inlet, wherein the water withinthe tank is heated by operation of the heating device thermally coupledto the water, the operation of the heating device is controlled by saidcontroller component, the method comprising: measuring, using thecold-water temperature sensor, successive incoming cold-watertemperatures in successive cold-water temperature measurements measuredin a defined measuring rate, detecting, by said controller component, abeginning of a tapping event when a difference of two successiveincoming cold-water temperatures of two successive cold-watertemperature measurements exceeds a predetermined first temperaturedifference threshold, measuring, using the cold-water temperaturesensor, successive incoming water temperatures during an adequate timeperiod after the beginning of said tapping event, deriving, using thecontroller component, the actual incoming water temperature as anaverage of the incoming water temperatures measured during said adequatetime period, determining, using the controller component, the thermalenergy content of the hot water tank device as a function of saidderived actual incoming cold-water temperature.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a relative inaccuracy of a mix water amount at differentincoming cold-water temperatures.

FIG. 2 shows the average ground water temperature in the US by location.

FIG. 3 shows a water storage system.

FIG. 4 shows a water storage system with a tilted heating device.

FIG. 5 shows a water storage system with a flow sensor.

FIG. 6 shows a result of a feedback of different water heater devices.

DETAILED DESCRIPTION OF EMBODIMENTS

It is to be understood that the figures and descriptions have beensimplified to illustrate elements that are relevant for a clearunderstanding of the present disclosure, while eliminating, for purposesof clarity, many other elements, which are conventional in this art.Those of ordinary skill in the art will recognize that other elementsare desirable for implementing the present disclosure. However, becausesuch elements are well known in the art, and because they do notfacilitate a better understanding of the present disclosure, adiscussion of such elements is not provided herein.

The present disclosure will now be described in detail on the basis ofexemplary embodiments.

For example, in the US there is a variation of the annual averageincoming water temperature by location of 40° F. as illustrated in FIG.2. A calculation shows in case of 15° C. incoming water temperature anda full loaded tank the customer gets 280 l mixed water out of the tank.If the incoming cold-water temperature changes from 15° C. to 10° C. theamount of hot water produced with the same tank is 30 l less than theindicated value. For an accurate energy monitoring device, it isimportant to take a variation of incoming cold-water temperature intoaccount or more if units are installed in a location where thetemperature of the incoming cold-water temperature differs from theestimated value. In the above example, the water volume in the tank is100 l and a set point for the water temperature in the tank is 85° C. Inthe context of the present disclosure, a “full loaded tank” or “fulltank” is a tank for which the water temperature is heated to theexpected hot water temperature, i.e. the set point of 85° C. in theabove example.

The following graph FIG. 1 shows the inaccuracy of the indicated mixwater amount if an estimated incoming cold-water temperature of 15° C.is considered. The example is basing on a 300-l tank with an integralsensor and 60° C. hot water temperature setting.

Referring to FIG. 1 the following is cited as an example. If theincoming water temperature is 15° C., the deviation of the displayedmixed water amount is 0.

If the tank has a load status of 0.5, that means the tank is half empty,the effective available amount of usable hot water is 20% less for 8° C.cold-water and 14% less for 10° C. incoming cold-water in comparison tothe displayed amount.

If the incoming cold-water temperature is 25° C. and the tank is 50%empty, the displayed amount of mixed water is 28% less than the amount,which is actually available.

The energy monitoring system has a higher accuracy under considerationof alternating seasonal incoming cold-water temperatures, and a standardenergy monitoring device is offered for different locations fromnorthern to southern climates. The higher accuracy is established if theincoming cold-water temperature is measured using a temperature sensorwhich needs to be located close to the incoming cold-water inlet tube.

The embodiment describes a system, which controls the energy content ofa water tank using an integral sensor, and an additional sensor locatedclose to the incoming cold-water tube. Preferably, the additional sensoris a cold-water temperature sensor.

FIG. 3 shows schematically and exemplarily a hot water tank device,which is also referred to as a water storage system. The hot water tankdevice comprises a tank 1 with a hot water outlet pipe 2, an incomingcold-water inlet pipe 3, a heating device 4, an electronic device 5, adisplay 6 and an actuator panel 7. There is optionally a flow sensor 106provided to measure the flow of water into the tank 1.

With this flow sensor 106 the exchange of water in the tank is measureddepending on the amount of tapped water in a time period that couldaffect the set point temperature.

Display 6 and actuator panel 7 can be implemented as actual physicaldevices, for instance on the outside of the hot water tank device. Justas an example, display 6 and actuator panel 7 can comprise a touchsensitive LCD screen to integrate the functions of displaying andadjusting the device, while also all other display and actuationalternatives known in the art can be used.

Alternatively or additionally, display 6 and actuator panel 7 can beimplemented remotely, for instance using a downloadable App whichcommunicates wirelessly with electronic device 5.

There are several temperature sensors 8, 9, 10 mounted to the tank 1.The temperature sensor 8 situated close to the pipe where the hot waterleaves the tank, an integral temperature sensor 9, which is mounted in avertical direction of the tank 1 in order to create a thermocouple chainof a multiple sensor elements, and a bottom temperature sensor 10situated close to the bottom incoming cold-water port. The electronicdevice 5 is connected to the heating device 4 to bring the heatingdevice 4 into operation if the water needs to be heated. In thisembodiment, the heating device is an electric heating element. Inanother case, it could additionally or alternatively be a heat exchangerof a heat pump or the tank 1 is connected to a heat pump or refrigerantcircuit. The tank 1 preferably comprises or consists of steel, whereinalso other materials are contemplated.

A safety cut-out is required to shut the heating device 4 down in caseof a failed electronic control 5 or temperature sensor 8, 9, 10failures. The safety cut-out is not shown in FIG. 3. All temperaturesensors 8, 9, 10 may be mounted on the tank surface using a tape orusing welded sensor sleeves which are in contact with water onwell-placed spots.

The electronic device 5 in one embodiment comprises a microcontroller,which controls the amount of usable hot water in the tank 1 bycontrolling heating device 4. The amount of usable hot water in the tank1 is determined using the equation [0]. The temperature differencebetween a temperature measured by temperature sensor 8 and a temperatureset point is calculated. The temperature set point is adjustable on theactuator panel 7, for instance. The energy content of the tank 1 isrecorded in energy units [KWh] and the temperature difference isdetermined between a measured temperature and the temperature setting.Electronic device 5 is configured to store a parameter indicating theincoming cold-water temperature. The incoming cold-water temperature iscrucial for determining the amount of usable hot water in the tank 1 andalso to determine the load status of the tank.

The thermal conductivity of the steel tank 1 surface and the thermalconductivity of the water transfer heat from the heated top section 101above the heating device 4 to the cold bottom section 102 of the tank 1,such that also a cold sump 103 is heated. This creates an inaccuratemeasurement result of the incoming water temperature if the temperaturedetermined by temperature sensor 10 is considered the cold-watertemperature. Also, depending on the incoming cold-water pipe 3 sectionbetween the water storage tank 1 and an entrance of a pipe into abuilding where the water tank 1 is installed more or less heat getstransferred from the ambient conditions to the cold-water, which warmsup the water in a tube section 104, cf. FIG. 4.

The actual incoming cold-water temperature needs to be detected with thefollowing steps which are integrated in the microprocessor software aspart of the electronic device 5 including an electronic main board.

1. Identify a tapping event with an adequate time period in order todetect the actual cold-water temperature by comparison of successivecold-water temperature values using the temperature information ofsensor 10 and a time base of 5 seconds.

2. Tapping begin is detected if the difference of two successivecold-water temperature values determined by temperature sensor 10 ismore than a defined first temperature difference threshold, for example2 K. Start a first timer 20 when tapping begin is detected.

3. Timer 20 compares the successive measured cold-water temperaturevalues periodically, for instance with a time base of 2 seconds. If thedifference of two successive measured temperature values is less than asecond temperature difference threshold, for example less than 1 K,start a second timer 21.

4. Timer 21 detects the incoming cold-water temperature periodically,for instance every 2 seconds, for a time period exceeding a minimumduration, for example a time period of more than 10 seconds, and putseach single following temperature value in a register. The storing in aregister is disclosed as one example Timer 21 and 20 are running inparallel and if the comparison of successive measured values shows adifference exceeding a third temperature difference threshold, which canfor instance be equal to the first temperature difference threshold suchas more than 2 K, both timers are stopped and the measurement isconsidered not valid. This would correspond to a situation in which thetemperature drop, which fell below the second temperature differencethreshold, would rise again, in other words, the water temperature wouldagain significantly drop, contrary to what is expected as a true oractual incoming cold water temperature.

5. If the measurement is considered valid, i.e. if the conditions forconsidering the measurement not valid in step 4 above do not apply,averaging the cold-water temperature values takes place by electronicdevice 5. It should be emphasized that any implementation of suchaveraging process as known in the art is contemplated.

6. Compare the current averaged cold-water temperature with the formerstored averaged value.

7. If the difference of the actual calculated value compared to theformer stored value is more than 2 K overwrite the former stored valueusing simple moving averaging process.

8. For initial start, a factory temperature value of 15° C. cold-watertemperature is stored.

The remaining energy content Q_(energy) in the tank is calculated usingthe following law or equation [2]:

Q _(energy) =M _(mcw) *CP _(Water)*(T _(mw) −T _(cw))  Equation [2]:

-   -   M_(m cw) amount of mixed water based on cold-water temperature    -   T_(mw) mix water temperature    -   CP_(water) specific heat capacity of water    -   T_(cw) temperature incoming cold-water

The energy content of the tank Q_(energy set point) is the energycontent if the thermostat of the tank is satisfied. It is calculatedwith the following equation [3]:

$\begin{matrix}{Q_{energyset} = {M_{m\mspace{14mu} {setpoint}}*CP_{Water}*\left( {T_{mw} - T_{cw}} \right)}} & {{Equation}\mspace{14mu}\lbrack 3\rbrack}\end{matrix}$

-   -   M_(m setpoint) amount of mixed water based on cold-water        temperature and setpoint temperature    -   T_(mw) mix water temperature    -   CP_(water) specific heat capacity of water    -   T_(cw) temperature incoming cold-water

The amount of energy Q_(energy reload) needed to be recharged iscalculated—equation [4]:

Q _(energy reloaded) =Q _(energy setpoint) *−Q _(energy)  Equation [4]:

The value of Q_(energy reload) is permanently calculated in the softwareof the electronic device 5.

The energy content information of the water tank is transmitted from theelectronic device 5 over line 13 to a ripple control transmitter device14, which can be connected to a structure like the internet.

For remote control, the ripple control tuner 12 is connected via line 11to the electronic device 5. Both devices 12 and 14 may be integratedwith the electronic device 5. It is an advantage to deliver the energycontent signal in form of a pulse pattern in a frequency range between110 Hz-2000 Hz.

This is an advantage because it is of interest to a grid owner to sortconsumers into different energy demand classes in order to be able tostabilize the voltage of the grid structure by remote control.

FIG. 6 shows the result of feedback of different water heater devicesconnected with a ripple control system. Due to the loading informationof each single water tank 1 system, the units get categorized in termsof their individual loading demand. For example, the number of verticallines in category [A] represent the number of consumers who need—or arecapable of receiving—a loading capacity of less than 2.5 KWh each. Thoseunits are transmitting their loading demand via their ripple controltransmitter a 110 Hz signal to the grid owner. Categories [B], [C] and[D] are categories for other loading capacity needs.

A tank 1 volume is also calculated.

A varied incoming cold-water flow is measured with a sensor.

An incoming cold-water temperature is a value, which is corresponding tothe actual water temperature of the cold-water source. This value couldbe determined by measuring the cold-water temperature by the waterutility in a water treatment facility or in a main feed line of theutility. This value is transmitted to the control unit where the energycontent of the water tank is calculated. Otherwise, it is an embodiment,that the cold-water temperature is measured in a water line of thebuilding where the water tank is located or in or at the water tank.

An embodiment of the sensor 10 is an at least single sensor element inclose distance to a water inlet 104. It could be mounted inside the coldsump 103 or at the bottom of the tank 1, at the water inlet 105, outsideor inside, or in the area of the tube section 104. In a special casewhere the incoming cold waterpipe 3 is situated through the top section101 of the tank 1, the sensor could be applied in the area of theincoming cold-water pipe 3 or other water inlet.

An embodiment of the integral sensor 9 is a chain of thermocouplesespecially in line, vertically mounted, a wound wire with a definedlength consisting of material with NTC or PTC characteristics, a layerwith a printed sensor or a multiple printed sensor chain or at least acouple of sensors in a series or parallel circuit. The integral sensoris located inside or outside the tank 1.

Data acquisition is realized by wire or wireless communication betweenthe temperature sensor 8, 9, 10 and the electronic device 5 or othercontrol unit.

The temperature sensor 10 should be installed at a place of the actualcold-water temperature. This place is in another embodiment one or morerepresentative locations where the temperature sensors 10 are located.If the temperature sensors 8, 9, 10 are mounted outside of the watertank 1 at a main water pipe or a house water pipe, it is an advantagewhen the temperature sensors 8, 9, 10 are connected to a wirelesscommunication transmitter to send the measured incoming cold-watertemperature to the control unit.

A further embodiment is to receive local cold-water temperature valuesfrom a utility or other source and actually store them in the electronicdevice 5 and to use them as cold-water temperatures instead of or inaddition to a measured temperature value from the cold-water incomingsensor 10. Otherwise, a cold-water temperature value can be entered tothe electronic device 5 by the user manually or via verbal command.

It is possible to retrofit existing water heating systems with thismethod.

While this disclosure has been described in conjunction with thespecific embodiments outlined above, it is evident that manyalternatives, modifications, and variations will be apparent to thoseskilled in the art. Accordingly, the preferred embodiments as set forthabove are intended to be illustrative, not limiting. Various changes maybe made without departing from the spirit and scope of the disclosure asdefined in the following claims.

It is noted that citation or identification of any document in thisapplication is not an admission that such document is available as priorart to the present disclosure.

1. A method of determining a thermal energy content of a hot water tankdevice, the hot water tank device comprising a tank, a cold-water inlet,a heated water outlet, a cold-water temperature sensor, a heating deviceand a controller component, the tank containing water, wherein the tankreceives incoming cold-water at the cold-water inlet and outputs heatedwater through the heated water outlet when a tapping event occurs, theheated water outlet being located in an upper portion of the tank andthe cold-water inlet being located in a lower portion of the tank withthe heating device being thermally coupled to water in between thecold-water inlet and the heated water outlet, the cold-water temperaturesensor being arranged in the lower portion of the tank configured todetermine a temperature of the water in vicinity of the cold-waterinlet, wherein the water within the tank is heated by operation of theheating device thermally coupled to the water, the operation of theheating device is controlled by said controller component, the methodcomprising: measuring, using the cold-water temperature sensor,successive incoming cold-water temperatures in successive cold-watertemperature measurements measured in a defined measuring rate,detecting, by said controller component, a beginning of a tapping eventwhen a difference of two successive incoming cold-water temperatures oftwo successive cold-water temperature measurements exceeds apredetermined first temperature difference threshold, measuring, usingthe cold-water temperature sensor, successive incoming watertemperatures during an adequate time period after the beginning of saidtapping event, deriving, using the controller component, the actualincoming water temperature as an average of the incoming watertemperatures measured during said adequate time period, determining,using the controller component, the thermal energy content of the hotwater tank device as a function of said derived actual incomingcold-water temperature.
 2. The method according to claim 1, wherein saidadequate time period starts when a difference of two successive incomingcold-water temperatures of two successive cold-water temperaturemeasurements is below a second temperature difference threshold.
 3. Themethod according to claim 1, wherein said adequate time period endsafter a predetermined period of time has elapsed or at or after an endof said tapping event.
 4. The method according to claim 1, wherein thestep of measuring successive incoming cold-water temperatures insuccessive cold-water temperature measurements with said cold-watertemperature sensor during said adequate time period comprises storingsaid successive cold-water temperatures in a storing unit of thecontroller component.
 5. The method according to claim 1, furthercomprising: determining, by said control unit, a validity of subsequentincoming water temperature measurements during said adequate timeperiod, wherein said subsequent cold-water temperature measurements arevalid if a temperature difference between the two subsequent cold-watertemperature measurements is lower than a third temperature differencethreshold.
 6. The method according to claim 1, the hot water tank devicefurther comprising a second temperature sensor mounted to said tank, themethod further comprising: measuring a tank temperature using the secondtemperature sensor, which is related to a thermal energy content, andoutput a tank temperature signal representative of said tank temperaturewith a tank temperature sensor mounted to said tank.
 7. The methodaccording to claim 1, further comprising a step of transmitting, using aripple control transmitter device in signal communication with thecontroller component, an energy content signal indicative of thedetermined thermal energy content.
 8. The method according to claim 7,further comprising a step of receiving, using a ripple control tuner insignal communication with the controller component, a signal foractivating the heating device in response to the energy content signal.9. A hot water tank device, the hot water tank device comprising a tank,a cold-water inlet, a heated water outlet, a cold-water temperaturesensor, a heating device and a controller component, the tank containingwater, wherein the tank receives incoming cold-water at the cold-waterinlet and outputs heated water through the heated water outlet when atapping event occurs, the heated water outlet being located in an upperportion of the tank and the cold-water inlet being located in a lowerportion of the tank with the heating device being thermally coupled towater in between the cold-water inlet and the heated water outlet, thecold-water temperature sensor being arranged in the lower portion of thetank configured to determine a temperature of the water in vicinity ofthe cold-water inlet, wherein the water within the tank is heated byoperation of the heating device thermally coupled to the water, theoperation of the heating device is controlled by said controllercomponent, the cold-water temperature sensor being configured tosuccessively measure incoming cold-water temperatures in successivecold-water temperature measurements in a defined measuring rate, thecontroller component being configured to determine a beginning of atapping event when a difference of two successive incoming cold-watertemperatures of two successive cold-water temperature measurementsexceeds a predetermined first temperature difference threshold, thecold-water temperature sensor being further configured to successivelymeasure incoming water temperatures during an adequate time period afterthe beginning of said tapping event, the controller component beingconfigured to derive the actual incoming water temperature as an averageof the incoming water temperatures measured during said adequate timeperiod, and the controller component being configured to determine thethermal energy content of the hot water tank device as a function ofsaid derived actual incoming cold-water temperature.
 10. A controllersystem for controlling a heat up of a hot water tank, comprising acold-water temperature sensor configured to be attached at a place of atank, which contains water and comprises a water inlet configured forreceiving incoming cold-water and a water outlet configured for allowingwater heated to exit, wherein said cold-water temperature sensor isconfigured to measure an actual incoming cold-water temperature and tooutput an actual cold-water temperature signal representative of saidactual incoming cold-water temperature and a control unit comprisingmicroprocessor software integrated in an electronic device, wherein saidcontrol unit is configured to receive said actual cold-water temperaturesignal transmitted by said cold-water temperature senor, wherein saidcontrol unit is configured to identify a tapping event and to control aheating device when said tapping event is identified in order to heatwater in the tank depending on a thermal energy content calculated as afunction of an actual incoming cold-water temperature measured by saidcold-water temperature sensor.
 11. A method of controlling a heat up ofa hot water tank having a control unit with a receiver interfacecircuit, a control circuit arrangement and a transmitter interfacecircuit, the method comprising the steps of: measuring a first tanktemperature of said hot water tank with a temperature sensor mounted tosaid hot water tank; receiving, by said receiver interface circuit, afirst tank temperature signal generated and transmitted by saidtemperature sensor, which represents said first tank temperature;generating, by said control circuit arrangement, an activation signal toactivate a heating device, when said control circuit arrangement callsfor heat; feeding an actual incoming cold-water temperature signal intosaid control circuit arrangement, wherein said actual incomingcold-water temperature signal represents an actual incoming cold-watertemperature of cold-water, which flows into said hot water tank;generating, by said control circuit arrangement, a parameter based onsaid actual incoming cold-water temperature signal; measuring a secondtank temperature of said hot water tank with said temperature sensorafter said incoming cold-water flowed into said hot water tank, whereinsaid second tank temperature is related to a thermal energy content ofsaid hot water tank; receiving, by said receiver interface circuit, asecond tank temperature signal generated and transmitted by saidtemperature sensor, which represents said second tank temperature;modifying, by said control circuit arrangement, said parameter based onsaid second tank temperature signal; performing, by said control circuitarrangement, a comparison of a set point value with said parameter,which is modified based on said second tank temperature signal;processing, by said control circuit arrangement, said activation signaldepending on said comparison; and transmitting, by said transmitterinterface circuit to a receiver interface circuit of a heating device,said activation signal, which is processed depending on said comparison.12. The method according to claim 11, further comprising: calculating,by said control circuit arrangement, an exact value of said thermalenergy content as a function of a reference mass and said parameter,which is modified based on said second tank temperature signal, whereinthe step of generating, by said control circuit arrangement, saidactivation signal depends on at least one of a) whether said exact valueis lower than said set point value and b) on an amount of said exactvalue, wherein said control circuit arrangement generates saidactivation signal when said exact value is lower than the set pointvalue.
 13. The method according to claim 11, wherein the step ofgenerating, by said control circuit arrangement, said activation signaldepends on whether said amount of said exact value is lower than aspecified value of thermal energy content, wherein said control circuitarrangement generates said activation signal when said amount of saidexact value is less than a specified value of thermal energy content.14. The method according to claim 11, further comprising: calculating,by said control circuit arrangement, an exact value of said thermalenergy content by multiplying a reference mass parameter by atemperature rise value, wherein said temperature rise value is adifference between said set point value and said incoming cold-watertemperature, wherein the step of generating, by said control circuitarrangement, said activation signal depends on said exact value.
 15. Themethod according to claim 11, further comprising: comparing, by saidcontrol circuit arrangement, said actual incoming cold-water temperaturerepresented by said actual cold-water signal fed into said controlcircuit arrangement with a previous stored water temperature representedby a previous stored water temperature signal, which is stored in astorage circuit of said control circuit arrangement; updating, by saidcontrol circuit arrangement, said previous stored water temperaturesignal, if said actual incoming cold-water temperature differs from saidprevious stored water temperature; and utilizing said stored watertemperature signal, which is updated, for the step of generating, bysaid control circuit arrangement, said parameter, wherein the step ofupdating, by said control circuit arrangement, said previous storedwater temperature signal, depends on whether said actual incomingcold-water temperature is lower than said stored water temperature,wherein said control circuit arrangement updates said previous storedwater temperature signal if said actual incoming cold-water temperatureis lower than said previous stored water temperature.
 16. The methodaccording to claim 11, wherein the step of feeding said incomingcold-water temperature signal into said control circuit arrangement,comprises the steps: measuring said actual incoming cold-watertemperature with a cold-water temperature sensor located in said hotwater tank close to a water inlet; and receiving, by said receiverinterface circuit, said actual incoming cold-water temperature signalgenerated and transmitted by said cold water temperature sensor, whichrepresents said actual incoming cold-water temperature.
 17. The methodaccording to claim 11, further comprising: comparing a last measuredincoming cold-water temperature with a previously measured incomingcold-water temperature to calculate a difference; and activating asecond timer, which initiates detecting said actual incoming cold-watertemperature or successive incoming cold-water temperatures with a timebase, when said difference is lower than a first defined differencevalue, after said second timer is started, detecting successive incomingcold-water temperatures periodically for a minimum duration of more than10 seconds and putting each incoming cold-water temperature in aregister; performing, by said control circuit arrangement, a comparisonof said successive incoming cold-water temperatures putted in saidregister; determining, by said control circuit arrangement, a validityof said successive cold-water temperature measurements depending on adifference resulting from said comparison, wherein said successivecold-water temperature measurements are valid if said difference islower than a second defined difference value; averaging, by said controlcircuit arrangement, the successive incoming cold-water temperaturesputted in said register to obtain an averaged incoming cold-watertemperature; comparing, by said control circuit arrangement, saidaveraged incoming cold-water temperature with a previous stored averagedwater temperature represented by a previous stored averaged watertemperature signal, which is stored in a storage circuit of said controlcircuit arrangement; and updating, by said control circuit arrangement,said previous stored averaged water temperature signal, if a differencebetween said averaged incoming cold-water temperature and said previousstored averaged water temperature is more than 2° C., wherein the stepof updating, by said control circuit arrangement, said previous storedwater temperature signal comprising a simple moving averaging process.18. The method according to the claim 11, further comprising: providingenergy needs of at least one hot water tank to an energy supplier ortransmitting energy needs of at least one hot water tank to a utilitycompany.
 19. The method according to claim 11, wherein a utility companysorting consumers into different energy demand classes in order tostabilize a voltage to keep said voltage constant, a frequency to keepsaid frequency constant, or both, of an electric grid.
 20. The methodaccording to claim 19, wherein the heating device comprises a receiverinterface circuit to receive a remote control command, which isgenerated and transmitted by a utility company, wherein the methodcomprises the step of receiving, by said receiver interface circuit ofthe heating device, said remote control command generated andtransmitted by said utility company.